What's your question? Ask

This is usually done in early spring after the threat of frost is gone. This article will give you more information: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm

You are correct. Good catch. For the word nerds out there, macrophylla means large (macro) leaves (phylla). Macrophilia means love of or attraction to (philia) something that is large (macro), often in reference to sexual fantasies of giants. OOPS!

I would only place one per pot to save you trouble later on with trying to separate them. This article will help: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-from-seed.htm

You can feed them both a high phosphorous and potassium fertilizer. They will both benefit from this. To keep the blue blooms on the hydrangea, you may have to do a little extra to them. Depending on the method that you choose, you might bring harm to the trees. This article will give you more information: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/change-hydrangea-color.htm

Hydrangeas are perennial to zone 3 but some subtypes are only hardy to zone 5. If it is currently in bloom, I would enjoy the bloom indoors. Don't try to plant it out until your frost free date has past. At that point, spend up to a week getting it used to outdoor conditions. Start with putting it in the shade for several hours and daily increase the light level and amount of wind it experiences. There are several types of hydrangea; if the plant tag doesn't tell you the 2 word Latin name or its cultivar name, call the florist. That info is necessary to determine how to care for your shrub, particularly when and how to prune it. The blue color is only evident when grown in acidic soil. In alkaline soil, the bloom turns pink. There are garden sulphur additions for lowering soil pH. Test soil where the shrub will be planted to know how much to add. Use a fertilizer for acid-loving plants. https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm

It is likely a large leaf hydrangia, which will flower on old growth only. This will mean that if it freezes and dies back, then it may not flower.

Alternatively, if it is not a large leaf, then it could be starting an infection. These spots would indicate that. It would be very helpful if you can post a photo. This will help me identify the problem better.

I recommend adding dolomitic lime and wettable sulfur around it. This will help kill off any infection, as well as provide the plant with some commonly deficient nutrients at the same time.

This article will help: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-not-blooming.htm